Dental hand piece



Dec. 9, 1947. M. sTAuNT DENTAL HAND PIECE 2 Sheets-Sheet l Filed Sept.14, 1945 Dec. 9, 1947. M sTAUN-r 2,432,179

DENTAL HAND PIECE 4 Filed Sept. 14, 1945 2 Sheets-Sheet 2 Patented Dec.9, 1.947

UNITED STATES PATENT OFFICE `DENTAL HAND PIECE Martin Staunt, Chicago,Ill. Applicationseptcmber 14, 19.45, Serial No. 616,195

(Cl. 32-26l 17 Claims.

The present invention relates to dentaltools, such as hand pieces, andis particularlyv concerned with theA provision of a dental hand piece ofthe high precision type.

@ne of the objects of the invention is the-provision of an improveddental hand piece which is provided with a particularly iine orsensitive chuck.

.Another object of the invention is 'the -provision of an improveddentalhand piece which is provided with an improved form of adjustment fordetermining the Vtightness of the grip of the chuck in. order to takeupwear on the chuck or the shank .which it is gripping,

Another 'object of Vthe-'invention is the provision of an improveddental hand piece structure by means of which provision is made totakeup the end play; as the end of the spindle and the thrust bearingmay wear.

Another object ofthe invention is thevprovision of an improved dentalhandpiece, the hand grip of which is provided with peripheralgrooves andsubstantially cylindrical knurled surfaces etween the grooves,which-provide a better grip on the hand piece forthefngersof theoperator.

Other objects and advantages of the invention will be apparent from thefollowingdescription and thel accompanying drawings, in which similarcharacters of reference-indicate similar parts throughout the severalviews.

Referring to the two sheets of drawings accompanying this specication,

Fig. 1 is an axial sectional view taken through ahand piece embodyingthe invention, with certain parts, such as the rear spindle, inelevation;

I Fig. 2 is a fragmentary View, similar to Fig. l, show'ng theydetailsof construction of the working end of the hand piece of Fig. 1 on ythesame plane, but on a larger scale;

Fig. 3 is a fragmentary View. similar'to Fig. 1, on ay larger scale,showing the details of construction of the rear end of the dentalhand-piece;

Fig. 4 is a side elevational view of a handpiece embodying theinvention;

Fig. 5 is a sectional view taken on-the plane of the line 5-5 of Fig. 2,looking inthe direction of the arrows;

Fig. 6 is a sectional view'taken on the plane of the line 6 6 of Fig. 2,lookingin the direction of the arrows;

Fig. 7 is a sectional view taken on vthe plane ofthe line l--l' of Fig.2, looking in the direction of the arrows;

Fig. 8 is. a .transverse sectional view taken on the plane of the line8-'-8 of Fig..` 2, looking in the direction of the arrows;

Fig. 9 is a transverse sectional View taken on the plane of the lineVQ-Q of Fig. 3, looking in the direction of the arrows;

Fig. `16v is a sectional view taken on the plane 2 of the line lillllof- Fig. 3, lookingin thedirection of the arrows; and

Fig. 11 is a sectional view `taken on .the vplane of -theline lvl--ll ofFig. 3, looking in the direction ofthe arrows.

Referring to Fig. 4, this is a side elevational view of lthe hand piece,andthe parts whichare visible are indicated bynumerals as followszflindicates the front bearing, 2| .indicates a` serrated vsheath whichservesasa handle, 22 indicated a sleeve member-which serves as aslidebearing for .the bearing.-3,. 23 indicates a slip jointV connectionsleeve which, connects to a flexible shaft housing. containing `theshaltthat drives the spindle-of the hand piece. lIn some embodimentscf theinvention thegpresent .hand piece maybe driven-byV means of a belt.

Lshall now describe the parts .which do not rotate with the shaft andtool.. beginningatthe right end of Figs. 1 and 3. lThe slipjointconnection sleeve 23 comprises a tubular metal member, having arectangular slot 24 that engagesa-lug on the exible shaft housing. Thissleeve .23 has aninwardly extending annular .ange..25, .serving asaithrust bearing for the spindle 26, which has a cylindrical enlargement21.

The sleeve `23 has threads on its left end, and it is adapted to bethreaded on the reduced threaded portion .284 of thev sleeve .memberY3i), whichhasa thrust surface 29 .engaging the other side of theenlargement 21 on the .spindle 26. The enlargement. 21 preferably Yconsists of ,an integral parteithe-spindleZG, which is provided with atransverse bore for receiving 'a pin to hold the spindle, while theVdrive sleeve. 23 is being threaded on the spindle, 26.

IThe bearing 3i] has a tubular bearing sleeve. 3l, which extendslongitudinalli7 of .the spindle-,as the sleeve has a bore for rotatablysupporting the spindle 26 for rotation. The threaded endof the slipjoint sleeve 23. isadapted tobe threaded home against anannular thrustsurface `on the bearing 3! so that `the bearing 30 and slip joint sleeve23 are iixedly secured together in such manner as tosupport the .spindle26 forrotation, butl to prevent axial movement of the spindle. i Y n Theslidingbearing sleeve 22 (Fig. 10). is provided with a slot 8l for,receiving a `key 32, which engages inthe slot 33 ofthe bearing sleeve.3|. Thus the sliding bearing. sleeve 22- is mounted for axial slidingmovement on the bearing -3Il, but is prevented from rotating relative,to -the bearing 3D.

The sliding bearing sleeve 22, comprising ra tubular metal member, hasan internal cylindrical bore B2, which has a slidingiit onYthe'fexternal cylindrical surface of lthe'bearing sleeveil. :At theright end of the slide bearing sleeve 22 there is a clearance 83,permitting axial movement-:of

formed with a ridge 84 between its ends so that Y the concave curvedsurface 85 serves as a finger grip for` gripping this sleeve when thechuck is to be actuated.

Toward the left of the annular ridge 84 the external surface of theslide bearing sleeve 22 is again tapered, and is provided with theexternal threads 86 on the cylindrical surface 81 for engagement withthe complementary threads 31 on the inside of the right end of theserrated sheath 2|.

The cylindrical portion 81 of the slide bearing sleeve 22 has a rotatingfit in the complementary cylindrical bore 88 in the sheath 2| so thatthe two engaging cylindrical surfaces 88 and 81 serve to maintain theaxial alignment between the sheath 2| and the slide bearing sleeve 22,which are xedly secured together by the threads 31, 86. The end of thesheath 2| engages an annular surface 89 on the slide bearing sleeve 22so that these may be threaded tightly together.

The sheath 2| is preferably provided with a multplicity of rectangularlyspaced peripherally extending grooves 90, which are partially circularin cross section, having no corners in which dirt may accumulate. Thisfacilitates the maintenance of sanitary conditions. The cylindrical landsurfaces 9| between the grooves 90 are preferably knurled for convenientgrip by the fingers of the operator.

The sheath 2| is of sucient length to house the major portion of themechanism of the hand piece. At the nose end of the instrument thesheath 2| supports the front bearing 20. For this purpose the frontbearing 20 has a reduced cylin drcal portion 9|, which has a tightfrictional fit in the bore 92 of the sheath.

The end of the sheath abuts against an annular shoulder 93, and there ispreferably a relief groove at 94 adjacent this shoulder on the frontbearing 20. The front bearing 20 comprises a tubular metal member, whichhas a cylindrical bearing bore 39, and this bore communicates with afrustoconical surface 40.

The external surface of the front bearing 20 is a tapered frustoconicalsurface 94, but at the point 95 the taper is increased and thefrustoconical surface 96 at the end of the bearing 20 is more sharp.

The inner frustoconical surface 40 communicates with a cylindrical bore91 in the end of the bearing for receiving the shank of a tool, such asa, burr. At a point intermediate the ends of the sheath 2| this sheathis provided with a radial bore 98 (Fig. 2) for receiving the stern 99 ofa headed member |00, which has a cylindrical head that is adapted to bereceived in the slot located in the end of an angular attachment used onsuch hand pieces to prevent rotation of the housing of the angularattachment.

The angular attachment has a tubular housing with a bore that engagesthe enlarged cylindrical portion on the sheath 2|, and the housing ofthe angular attachment also engages the frustoconical surface 94 of thebearing 20 with a cornplementary surf ace.

The sheath 2| also preferably supports a rear bearing |02 for the frontspindle, and this bearing may comprise a tubular cylindrical metalmember of hardened steel or suitable alloy having an externalcylindrical surface which fits in the counterbore |03 of the sheathagainst an annular shoulder |04.

The rear bearing 102 has an inner cylindrical surface |05 which engagesthe exterior of the front spindle 6|.

The front spindle member 6| comprises a tu- -bular metal member ofhardened steel or suitable alloy, which may be chromium plated on itsexternal bearing surfaces, the surfaces being ground and lapped untilthey have a, suitable t with the bearings in which they are used.

At its front end the spindle 6| is provided with a frustoconical endsurface |06, which engages the frustoconical inner surface 40 of thenose bearing 20. Extending backwardly from the frustoconical surface|06, the front spindle 6| has an external cylindrical surface |01, whichhas a bearing fit in the bearing bore 39 of the front bearing 26. Beyondthe front bearing and toward the rear of the instrument, the size of thefront spindle 6| is increased by a short, abrupt taper |01, and theexternal cylindrical surface |08 of the spindle is of sufcient size tohave a running fit in the bore |05 of the rear bearing |02.

Between the bearings the spindle 6| has, of course, a clearance withrespect to the sheath 2|. At its rear end the front spindle member 6|has a threaded bore |09, which is adapted to receive the complementarythreaded portion ||0 on the ball thrust member 36.

The ball thrust member 36 has a radially projecting flange with a thrustsurface ||2, against which the end of the front spindle 6| is tightlyengaged when it is threaded home, so that these two members 36 and 6|rotate together.

Referring now to the inside of the front spindle member 6|, this isprovided with a frusto-con ical surface 61 at the nose end forengagement with a complementary frusto-conical surface 10 on the collet65.

Extending backwardly inside the front spindle 6| from the frustoconicalsurface 61, there is a cylindrical bore ||3, which engages the externalcylindrical surfaces ||4, ||5, ||6 on the collet 65 and also engages theexternal cylindrical surface ||1 of a chuck plunger 64.

The collet 65 comprises a tubular metal member, which may be made ofsuitable steel, and which has bores 12 and 13 at each end ofapproximately the same size as the shank of the tool that is to begripped. Between the bores 12, 13 the collet 65 has an enlargedcounterbore 1|, providing a clearance.

On its external surface the collet 65 has clearance grooves 68 betweenthe cylindrical surfaces ||4, ||5 and ||6. At its ends it has thefrustoconical surfaces 10 and 69, and the latter engages with acomplementary inner frusto-conical surface 66 on the chuck plunger 64.

The clearance grooves 68 in the Vcollet give the end portions of thecollet greater flexibility, and the same is true of the enlargedcounterbore 1|.

Each end portion of the collet is provided with a plurality of axiallyextending grooves or slots 14, 15, preferably three in number, equallyspaced angularly about each end of the collet. These grooves 14, 15separate the end portions of the collet into three legs that may beforced together by the frustoconical surfaces '61 and 66 to grip theshank or stem of a tool.

The natural tendency of the end portions of the collet is to expand, dueto their own resiliency, thus releasing the stem or shank.

The chuck plunger 64 comprises a tubular metal member having anAexternalv cylindricallisu'rface which is adapted to slide in the bore||3 of the front spindle 6 I. -At its front end it has the innerfrustoconical surface 66, which engages the end of the collet and tendsto contract the collet when the chuck plunger 64 moves toward the leftin Fig. 2.

lThe chuck plunger 64 has a cylindrical bore H8,- which hasathreadedportion 51 for receiving the plunger vscrew 56. -The plungerscrew 56 comprises a cylindrical. threaded shank provided with asubstantially cylindrical head, having a plane thrust surface ||9.

The 'shank 56 ofthe plunger-screwhas its end providedA with a screwdriver slot 58- so that a suitable `small screw driver may be insertedin the end of the` hand piece to adjust the screw 56, thus adjusting theeffective length of the chuck plunger 64.

The vfriction involved in thefturning of the screw is suiiicient toretainits adjustment. The chuck `plunger 54 is prevented from rotatingby means of aheadless screw bolt 60,- whi'ch is threaded into a threadedbore |20 in the plunger 54, andhas a reduced cylindrical endportion |2|extending into a slot |22', which runs longitudinally of the inner wallof the spindle 6|.

In the preferred embodiment of the invention themember |2| may beranintegral radially extending cylindrical lug, forming an integral part ofthe plunger sleeve '64. Thus, .when the screw isbeing adjusted, theplunger 64 cannot turn.

v'The plunger.64 is adapted to'be actuated in an axial direction by aplunger actuating memberA 45, which comprises atubular metal memberhaving an external cylindrical surface |23, with a sliding fit in thecounterbore 62 of the spindle 6|.

At its frontend the member 45 has a frustoconicalsurface |24, and itsend portion 55 is plane so thatit may engage the plane end surface'|'.|9.of the screw. 56. The counterbore 62 iswsuiiicient in length andcommunicates with a irustoconic'al portion |25, complementary to thetapered `surface |24, so as to permit the actuating member 45a suicientrange. of axial movement.

Atits rearor right end (Fig. 2) thev actuating member 45 has an innerfrustoconical surface with a relatively steep slope, providing an acuteVangleat the rear edge of the actuating member 45. This frustoconicalsurface 59 is adapted to be engaged by the' balls 48, 49, which arecarried by a ball cage which is carried by the ball thrust member 36.

vThe ball thrust member 36 is provided at its left end with a pair ofaxially extending slots, one for each ball 48 and 49, the bore |39defining the base of each slot, which may be partially circular whenviewed in elevation, so that these slots engage the balls 48, 49.

-The slots |39 preferably receive more than `half of the balls 48, 49 sothat there is no tendency forthe. bals to be cammed out of the slots.The purpose of the slots |30 is tov provide a direct drive between theball thrust member 36 and the ballsninstead of depending solely on thecage 5|, which might at rsome time become loose. The left endof the ballthrust member 36 may conform in shape to the inner surface of the ballcage 5|.

.Theball thrust member 36 has been referred to ashavinga threadedsurface I I0, which engages theninner threads |09 on the Spindle 6|.This ball thrustmember36 isa tubular metal `member, havinganinternal.cylindricalrfbore I26. At its front en'd it `has a reducedcylindrical vportion |21, which hasa tight frictional i'lt With-thethrust ball cage 5|.

The thrust ball cage 5| comprises a sheet metal tubular member ofsubstantially cylindrical shape, havingan inwardly `turnedcurved ange,which is provided with a centrally located bore |28 for passing acammember 43, and also having a plurality, suchas, for example, twolateral slots |29 of suicient size to receive the balls 43, 49,. butalso permitting these ballsto project into the bore |28, whileretainingthe balls against axial movement of the cage.

The balls 48, 49 are thus engaged by the cage and the walls of thegroovesi |39 .of .the ball thrust .memben and are held in properposition to move radially with respect to. the ball thrust member. Theballs, ball cage, and ballthrust member 36 are held againstA axialmovement by being secured to the spindle by the threads |99, H0.

The cam member 43 comprises a substantially cylindrical metal member,which is provided on its diametrically opposite sides withV a pair ofgrooves 46, 41, the grooves being partially circular in cross sectionand tapering in depth from the right portion of the cam member'y 43 inFig. 2 to the left end of this cam.

In every case the grooves are of suitable cross section to have arolling t with the balls 48,' 49. The cam member 43 is adapted to bemoved axially in the bore |26; and when it moves axially, the balls 48,49 are cammed kinwardly or outwardly by the walls vof the grooves-46,f41.

Referring now to Fig. 3, the right end of the cam member 43 is thereshown as being provided with a reduced circular portion |3|, which ispartially spherical in shape, the lateral surface |32 being curved sothat itis circular in cross section, as shown.

This permits the end of the camming member 43 toV have a` limitedpivotal motion in the bore |32, in which it is secured by a through pin|33, which passes through bores inthe cam member 43 and the rear spindle26, the ends of the pin being riveted over, or the pin being retained inplace by engagement of its ends with the walls 0f the bore |34 in therear bearing 3|.

The rear spindle 26 comprises a substantially cylindrical metal member,having the bore |32 at one end and having an enlargement 21, previouslydescribed, adjacent the other end, to serve as a thrust bearing, thisenlargement being provided with a, reduced driving shaft |35 that may bepinned in the enlargement 21 in a way similar to the pin |33 and cam 43in the bore |33.

The reduced drive shaft |35 has a Ytaperedror frustoconical shoulder |36and a threaded portion |31 so that the sleeve 23, which has a threadedbore |38, may be threaded tightly on the drive shaft |35. The sleeve 23isl provided with a tapered slot |39 in its right end, leaving a pair oflegs that provide a driving engagement with a flexible drive shaft, andthe sleeve 23 may also be provided with the slot |49 for engagement witha screw driver, when this sleeve is be ing threaded on the spindle 26.

The bearing is preferably provided with a relief groove at |4| adjacentthe annular thrust surface |42 or the clearance space 83. The rearspindle 26 preferably has a pair of cylindrical portions |43, |44separated by the relief groove r portion of reduced diameter |45.

The range of movement of the chuck actuating member 22 may be regulatedby the adjustment of a threaded end thrust adjuster 34 carried by theactuating member 22. For this purpose the actuating member 22 may haveits left end provided with threaded bore 35, into which the threadedsleeve 34 is threaded, and the space between the end of the sleeve 34and the annular flange determines the range of movement of the actuatingmember 32.

The operation of my hand piece is as follows: When the sleeve 23 isconnected to the housing of a flexible shaft and the exible shaft is inengagement with the rear spindle 26 at the sleeve 23, the rear spindlewill be caused to rotate within the bearing 3|, carrying with it the cammember 43.

The sleeve 23, chuck actuating member 22, sheath 2|, and front bearing2l) do not rotate, but are held by the hand of the operator. The cammember 43 transmits its rotative motion to the balls 48, 49, which inturn transmits rotative motion to the cage 5| and the ball thrust member36, which is secured to the front spindle 6|.

The front spindle also rotates, carrying with it the actuating sleeve 45and the plunger 64 and collect 65, all of which latter parts are carriedby the front spindle 6|.

When the chuck is to be opened, the actuating member 22 is pushed towardthe right in Fig. 1 with respect to the sleeve 23. This causes aneffective shortening of the outer housing and causes the balls 4'8, 49to be moved toward the right into the deeper part of the grooves 46, 41.As the balls move into a deeper part of the grooves they relievepressure on the frustoconical surface 50 and permit the plunger' 45 tomove toward the right, which relieves the pressure on the tapered endsof the collect at the frustoconical surfaces 6l, 66 so that the colletmay open by virtue of its own resiliency.

When the collet is to be closed, the actuating member 22 is pulled awayfrom the annular shoulder |42, tending to open the clearance space 83,effectively increasing the overall length of the outer housing of thehand piece. This causes the rear spindle to withdraw the cam 43 towardthe right with respect to the balls 48, 49, a more shallow part of thegroove camming the balls apart in their cage.

As the balls are cammed apart they move radially and engage thefrustoconical surface 50, camming the sleeve 45 toward the left, whichin turn urges the plunger 64 toward the left and places an axialpressure on the collet 85.

Axial pressure on the collet at the frustoconical surfaces 66, 61 causesthe end portions of the collet to be cammed toward each other, effectinga grip on a shank or stem in the collet.

When it is desired to regulate the length of the internal assembly, thatis, the collet and its actuating members inside the spindle 6|, a screwdriver is inserted in the bore 97 into engagement with the slot 58, andthe length of this assembly may be increased or decreased by turning thescrew bolt 56 with respect to the sleeve 64, the sleeve being heldagainst rotation by the screw -bolt B0.

It will thus be observed that the chuck may be so adjusted that a veryslight movement of its actuating members will cause it to grip the shankof the tool. Any wear that occurs can be taken up, and the chuck can bekept constantly in the best and most sensitive gripping position.

It will thus be observed that I have invented an improved dental handpiece, which is very ne and sensitive in its gripping action, and whichmay be used for a long period of time without any of its parts becomingloose because the wear can be taken up. The bearings which support thespindles may be lapped and ground very accurately so that they arepractically in perfect axial alignment, and the present hand piece isadapted to run more smoothly and with less vibration than with any ofthe devices of the prior art.

The tightness of grip of the chuck can be adjusted as desired either tosuit the individual needs of the user or to take up wear or end play onthe end of the spindle. The sheath is provided with partially circularperipheral grooves, within which there are no corners in which dirt maybel caught, yet the hand piece may be gripped without any possibility ofslipping in the hand.

While I have illustrated a preferred embodiment of my invention, manymodifications may be made without departing from the spirit of theinvention, and I do not wish to be limited to the precise details ofconstruction set forth, but desire to avail myself of all changes withinthe scope of the appended claims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States, is:

l. In a collet closing mechanism, the combination of a spindle having acylindrical bore for receiving the collet, said spindle having at itsend an inner tapered surface, a collet slidably mounted in said bore andhaving a tapered end surface for engaging the inner tapered surface inthe spindle, said collet having slotted and tapered end portionsprovided with a through bore, an actuating plunger slidably mounted inthe bore of said spindle, said plunger having an inner tapered surfaceengaging the other tapered end surface of the collet, threaded meanscarried by said plunger for adjusting the effective length of theplunger, and an actuating sleeve carried in a counterbore in saidspindle for engaging said threaded means to move said plunger in anaxial direction, said actuating member being provided With afrustoconical camming surface on its opposite end, and anti-frictionmeans adapted to be moved radially inward or outward to engage saidlatter camming surface to move the actuating member in an axialdirection to open or close the collet.

2. In a collet closing mechanism, the comblnation of a spindle having acylindrical bore for receiving the collet, said spindle having at itsend an inner tapered surface, a collet slidably mounted in said bore andhaving a tapered end surface for engaging the inner tapered surface inthe spindle, said collet having slotted and tapered end portionsprovided with a through bore, an actuating plunger slidably mounted inthe bore of said spindle, said plunger having an inner tapered surfaceengaging the other tapered end surface of the collet, threaded meanscarried by said plunger for adjusting the effective length of theplunger, an actuating sleeve carried in a counterbore in said spindlefor engaging said threaded means to move said plunger in an axialdirection, said actuating member being provided with a frustoconicalcamming surface on its opposite end, and anti-friction means adapted tobe moved radially inward or outward to engage said latter cammingsurface to move the actuating member in an axial direction to open orclose the collet, said anti-friction means comprising a pair ofdiarnetrically located balls, means for retaining the balls, and anelongated oamming member having axially extending grooves of taperingdepth, whereby the balls are moved radially when the camming member ismoved axially, said means for retaining the balls comprising a cage anda supporting sleeve, said cage having a central bore for passing thecam, and radial slots for receiving and holding the balls.

3. In a dentalhand piece, the combination of a sheath comprising anelongated tubular metal member, said sheath having a bearing at itsfront end and being slidably mounted on the exterior of a bearing at itsrear end, with a tubular housing member carried by said latter bearingand adapted to be secured to a flexible shaft, a front spindle rotatablymounted in the bearing at the front end of said sheath and also carriedby a bearing intermediate the ends of said sheath, and a rear spindlerotatably mounted in the rear bearing, a collet for gripping the shankof a tool in the front end of said spindle, and common actuating meansfor rotating said spindle and opening or closing said collet,connectingv said rear spindle and said front spindle, said commonactuating means including a cam member carried by saidrear spindle, saidcam member having a pair of diametrically opposite tapered groovesextending longitudinally of said cam member in said front spindle, and apair of balls located in said grooves and carried by said front spindle,said balls being movable radially by engagement in the tapered groovesof said cam member and engaging an actuating member which is movedlongitudinally by the balls to open or close the collet.

4. In a dental hand piece, the combination of a sheath comprising anelongated tubular metal member, said sheath having a bearing at itsfront end and being slidably mounted on the exterior of a bearing at itsrear end, with a tubular housing member carried by said latter bearingand adapted to be secured to a iiexible shaft, a front spindle rotatablymounted in the bearing at the front end of said sheath and also carriedby a bearing intermediate the ends of said sheath, and a rear spindlerotatably mounted in the rear bearing, a collet for gripping the shankof atool in the front end of said spindle, and common actuating meansfor rotating said spindle and opening or closing said collet, connectingsaid rear spindle and said front spindlesaid common actuating meansincluding a cam member carried by said rear spindle, said cam memberhaving a pair of diametrioally opposite tapered grooves extendinglongitudinally of said cam member in said .front spindle, and a-pair ofballs located insaid grooves and carried by said front spindle, saidballs being movably radially by enf gagement ,in thetapered grooves ofsaidY cam member and engaging an actuating member which is movedAlongitudinally by the balls to open or `close Athecollet, saidactuating member having an inner. fr usto-,conical surface engagingsaidballsl,

5.' Ina dentalhand piece,v the. combination.- Yof asheath comprisinganlelongated tubular metal member,v said sheath having a bearing at .itsiront end and being slidably mounted on the exterior of a bearing at itsrear end, with a tubular housing member carried by said 'latter bearingAand adapted to be secured to a fiexible shaft, a front spindlerotatably mounted in the bearing at the front end of said sheath andalsoo carried by a bearing intermediate the ends of said sheath, .and arear spindle rotatably mounted in the rear bearing, a collet forgripping the shank of .a toolin the front end of said spindle, andcommon actuating means for rotating said spindle and opening or closingsaid collet, connecting said rear spindle and said front spindle, saidcommon actuating means including a cam member carried by said rearspindle, said cam member having a pair of diametrically opposite taperedgrooves extending longitudinally of said. cam member in said frontspindle, and a pair of balls located in said grooves and carried by saidfront spindle, said balls being movable radially by engagement .in thetapered grooves of said cam member and engaging an actuating memberwhich is moved longitudinally by the balls to open or close the collet,said actuating member having an inner frustoconical surface engagingsaid balls, saidY actuating member engaging a plunger and said plungerengaging said collet;

6.. In a dental hand piece, the combination of a sheath comprising anelongated tubular metal member, said sheathhaving a bearing at its frontend and being slidably mounted on the exterior of .a bearing at its rearend, with a tubular housing member carried by said latter bearingandadapted to be secured to a flexible shaft, a front spindle rotatablymounted inthe bearing at the front end vof said sheath and also carriedby a bearing intermediate the ends of said sheath, and a rear spindlerotatably mounted in the rear bearing,.a collet for gripping the shankof a tool in .the front end of said spindle, and common actuating,meansv for rotating said spindle and opening or closing said collet,connecting said rear spindle and said front spindle, said commonactuating means including a cam member carried by said rear spindle,said cam member having apair of. diametrically opposite tapered groovesextending longitudinally of said cam member in said frontv spindle, anda pair of balls located in said grooves and carried by said frontspindle, said balls being movable radially by engagement in the taperedgrooves of said cam member and engaging an actuating member which ismoved longitudinally by the balls to open or close the collet, saidactuating member having an inner irustoconical ,surface engaging saidballs, said actuating` member engaging a plunger, and said plungerengaging said collet, said plunger having a pair of complementarilythreaded portions whereby the effective length of the plunger may beadjusted to adjust the gripping action of the collet and to take upwear.

7. In a dental hand piece, the combination of a sheath comprising anelongated tubular metal member, said sheath having a bearing at itsfront end and being slidably mounted on the exterior of abearing at itsrear end, with a tubular housing member carried. by said latter bearingvand adapted to be secured to a flexible shaft, a front spindle rotatablymounted in the'bearing at the front end of said sheath and also carriedby a bearing intermediate the ends of said sheath, and a rear. spindlerotatably mounted in the rear bearing, a collet for gripping the shankof a tool in the front end of said spindle, and common actuating meansfor rotating said spindle and opening or closing said collet, connectingsaid rear spindle and said front spindle, said common actuating meansincluding a cam member carried by said rear spindle, said cam memberhaving a pair of diametrically opposite tapered grooves extendinglongitudinally of said cam member in said front spindle, and a pair ofballs located in said grooves and carried by said front spindle, saidballs being movable radially by engagement in the tapered grooves ofsaid cam member and engaging an actuating member which is movedlongitudinally by the balls to open or close the collet, said actuatingmember having an inner frustoconical surface engaging said balls, saidactuating member engaging a plunger, and said plunger engaging saidcollet, said plunger havin a pair of complementarily threaded portionswhereby the effective length of the plunger may be adjusted to adjustthe gripping action of the collet and to take up wear, one' of saidthreaded members being provided with a slot accessible by a screw driverextending into said hand piece through said collet.

8. In a dental hand piece, the combination of a sheath comprising anelongated tubular metal member, said sheath having a bearing at itsfront end and being slidably mounted on the exterior of a bearing at itsrear end, with a tubular housing member carried by said latter bearingand adapted to be secured to a flexible shaft, a front spindle rotatablymounted in the bearing at the front end of said sheath and also carriedby a bearing intermediate the ends of said sheath, and a rear spindlerotatably mounted in the rear bearing, a collet for gripping the shankof a tool in the front end of said spindle, and common actuating meansfor rotating said spindle and opening or closing said collet, connectingsaid rear spindle and said front spindle, said common actuating meansincluding a cam member carried by said rear spindle, said cam memberhaving a pair of diametrically opposite tapered grooves extendinglongitudinally of said cam member in said front spindle, and a pair ofballs located in said grooves and carried by said front spindle, saidballs being movable radially by engagement in the tapered grooves ofsaid cam member and engaging an actuating member which is movedlongitudinally by the balls to open or close the collet said actuatingmember having an inner frustoconica1 surface engaging said balls, saidactuating member engaging a plunger, and said plunger engaging saidcollet, said plunger havin a pair of complementarily threaded portionswhereby the effective length of the plunger may be adjusted to adjustthe gripping action of the collet and to take up wear, one of saidthreaded members being provided with a slot accessible by a screw driverextending into said hand piece through said collet, and means forpreventing relative rotation between said plunger and said frontspindle.

9. In a dental hand piece, the combination of a sheath comprising anelongated tubular member with a front end bearing and a rear bearingxedly secured to said sheath, a tubular spindle rotatably mounted insaid bearings and including at its rear end a ball thrust member fixedlysecured in said spindle, and having an axial bore, a driving memberextending through said axial bore into said spindle, and having a pairof ax- 4ially extending partially circular grooves tapered in depthtoward the front end of said member,

a pair of balls, one in each of said grooves, and adapted to be engagedby said ball thrust member, said ball thrust member having radialshoulders engaging said balls and adapted to transmit the drive fromsaid driving member to said spindle through said balls.

10. In a dental hand piece, the combination of a sheath comprising anelongated tubular member with a front end bearing and a rear bearingxedly secured to said sheath, antubular spindle rotatably mounted insaid bearings and including at its rear end a ball thrust member iixedlysecured in said spindle, and having an axial bore, a driving memberextending through said axial bore into said spindle, and having a pairof axially extending partially circular grooves tapered in depth towardthe front end of said member, a pair of balls, one in each of saidgrooves, and adapted to be engaged by said ball thrust member, said ballthrust member having radial shoulders engaging said balls and adapted totransmit the drive from said driving member to said spindle through saidballs, said balls being retained in place in said grooves and engagingsaid ball thrust member by a cage secured on said ball thrust member,said cage having slots for receiving the balls and surfaces for holdingsaid balls against said ball thrust member.

l1. In a dental hand piece, the combination of a sheath comprising anelongated tubular memberv with a front end bearing and a rear bearingxedly secured to said sheath, a tubular spindle rotatably mounted insaid bearings and including at its rear end a ball thrust member iixedlysecured in said spindle, and having an axial bore, a driving memberextending through said axial bore into said spindle, and having a pairof axially extending partially circular grooves tapered in depth towardthe front end of said member, a pair of balls, one in each of saidgrooves, and adapted to be engaged by said ball thrust member, said ballthrust member having radial shoulders engaging said balls and adapted totransmit the drive from said driving member to said spindle through saidballs, said driving member having its forward end surrounded by atubular actuating member provided with a frusto-conical surface forengagement with the forward side of said balls, and said actuatingmember being adapted to actuate a collet chuck located in said spindle.

12. In a dental hand piece. the combination of a sheath comprising anelongated tubular member with a front end bearing and a rear bearingxedly secured to said sheath, a tubular spindle rotatably mounted insaid bearings and including at its rear end a ball thrust member xedlysecured in said spindle, and having an axial bore, a driving memberextending through said axial bore into said spindle, and having a pairof axially extending partially circular grooves tapered in depth towardthe front end of said member. a pair of balls, one in each of saidgrooves, and adapted to be engaged by said ball thrust member, said ballthrust member having radial shoulders engaging said balls and adapted totransmit the drive from said driving member to said spindle through saidballs, said driving member having its forward end surrounded by atubular actuating member provided with a frusto-conical surface forengagement with the forward side of said balls, and said actuatingmember being adapted to actuate a collet chuck located in said spindle,and a threaded adjustable member located between said collet chuck andsaid actuating member and having a screw driver slot accessible throughthe forward end of said handpiece, whereby the collet may be adjusted byadjusting the position of said threaded member.

13. In a dental hand piece, the combination of a sheath comprising anelongated tubular member with a front end bearing and a rear bearingxedly secured to said sheath, a tubular spindle rotatably mounted insaid bearings and including at its rear end a ball thrust member xedlysecured in said spindle, and having an axial bore, a driving memberextending through said axial bore into said spindle, and having a pairof axially extending partially circular grooves tapered in depth towardthe front end of said member, a pair of balls, one in each of saidgrooves, and adapted to be engaged by said ball thrust member, said ballthrust member having radial shoulders engaging said balls and adapted totransmit the drive from said driving member to said spindle through saidballs, a drive shaft rotatably mounted in the rear end of said sheath,and a universal connection between said driving member and said driveshaft.

14. In a dental hand piece, the combination of a sheath comprising anelongated tubular member with a front end bearing and a rear bearingxedly secured to said sheath, a tubular spindle rotatably mounted insaid bearings and including at its rear end a ball thrust member fixedlysecured in said spindle, and having an axial bore, a driving memberextending through said axial bore into said spindle, and having a pairof axially extending partially circular grooves tapered in depth towardthe front end of said member, a pair of balls, one in each of saidgrooves, and adapted to be engaged by said ball thrust member, said ballthrust member having radial shoulders engaging said balls and adapted totransmit the drive from said driving member to said spindle through saidballs, a drive shaft rotatably mounted in the rear end of said sheath,and a universal connection between said driving member and said driveshaft, said connection comprising a cylindrical socket in said driveshaft, a partially cylindrical ball-shaped formation on said drivingmember in said socket, and a transverse pin carried by said formationengagin-g in apertures in the walls of said socket.

15. In a dental hand piece, the combination of a sheath comprising anelongated tubular member with a front end bearing and a rear bearingxedly secured to said sheath, a tubular spindle rotatably mounted insaid bearings and including at its rear end a ball thrust member xedlysecured in said spindle, and having an axial bore, a driving memberextending through said axial bore into said spindle, and having a pairof axially extending partially circular grooves tapered in depth towardthe front end of said member. a pair of balls, one in each of saidgrooves, and adapted to be engaged by said ball thrust member, said ballthrust member having radial shoulders engaging said balls and adapted totransmit the drive from said driving member to said spindle through saidballs, said ball thrust member having a reduced cylindrical portion anda ball retaining cage having a pressed t on said cylindrical portion andhaving slots for receiving said balls, said slots extending radially topermit the balls to move radially in said grooves.

16. In a dental hand piece, the combination of a sheath comprising anelongated tubular member with a front end bearing and a rear bearingxedly secured to said sheath, a tubular spindle rotatably mounted insaid bearings and including at its rear end a ball thrust member iixedlysecured in said spindle, and having an axial bore, a driving memberextending through said axial bore into said spindle, and having a pairof axially extending partially circular grooves tapered in depth towardthe front end of said member. a pair of balls, one in each of saidgrooves, and adapted to be engaged by said ball thrust member, said ballthrust member having radial shoulders engaging said balls and adapted totransmit the drive from said drivin-g member to said spindle throughsaid balls, said ball thrust member having a reduced cylindrical portionand a ball retaining cage having a pressed t on said cylindrical portionand having slots for receiving said balls, said slots extending radiallyto permit the balls to move radially in said grooves, and a colletactuating member having an inner frustoconical surface engaging theballs on a Side opposite to said ball thrust member, whereby a radialmovement of the balls causes an axial movement of the collet actuatingmember.

17. In a dental hand piece, the combination of a sheath comprising anelongated tubular member with a front end bearing and a rear bearingxedly secured to said sheath, a tubular spindle rotatably mounted insaid bearings and including at its rear end a ball thrust member xedlysecured in said spindle, and having an axial bore, a driving memberextending through said axial bore into said spindle, and having a pairof axially extending partially circular grooves tapered in depth towardthe front end of said member, a pair of balls, one in each of saidgrooves, and adapted to be engaged by said ball thrust member, said ballthrust member having radial shoulders engaging said balls and adapted totransmit the drive from said driving member to said spindle through saidballs, said ball thrust member having a reduced cylindrical portion anda ball retaining cage having a pressed t on said cylindrical portion andhaving slots for receiving said balls, said slots extending radially topermit the balls to move radially in said grooves, and a colletactuating member having an inner frustoconical surface engaging theballs on a side opposite to said ball thrust member, whereby a radialmovement of the balls causes an axial movement of the collet actuatingmember, said collet actuating member having a bore for slidablyreceiving said driving member.

MARTIN STAUNT.

REFERENCES CITED The following references are of record in the iile ofthis patent:

UNITED STATES PATENTS Number Name Date 1,380,716 Herman June 7, 19211,741,734 Pannwitz Dec. 31, 1929 Re. 15,681 Porter Aug. 21, 19231,427,286 Graves Aug. 29, 1922 552,669 Pedersen Jan. 7,1896

